www.bootdisk.com
reviewed and fixed a typo on February 26, 2016 and I still enjoy the read
Using the fdisk utility to set up hard drives
It's one of the more difficult utilities to explain and learn how to use
especially if you need to delete partitions with it. The basic problem is
learning what the terms mean, for example, Primary partition, Extended
partition, Logical drive, Active partition.
But once you learn and understand what the terms are you can use ANY
partition program. So, I wrote this analogy which I believe explains things
quite well, so even a beginner can understand what a partition is and how
to use fdisk or other programs that deal with setting up your hard drive.
Let's begin:
Suppose you just bought a 100 by 100 foot lot for your retirement home
in Florida. The developer put a road through an old sod farm and put up a
sign for the lot you bought called Lot B. You go to see your lot and all
you see is the sign next to the road and a large field of grass. If you
take a closer look, you can see the steel pipes or wooden property markers
that the surveyors used to define your lot.
This is analogous to what your hard drive looks like when you buy it new
or have deleted all the partitions. The X's would be the property markers.
Exibit A. New hard drive / aka Lot B
X X
No partitions - No Drive letters
X X
A computer needs to put data on the hard drive, but is not smart enough
to find the property markers. An analogy would be you need to have the
lumber yard deliver some wood for your new home. The delivery guy finds
the Lot B sign but only sees the old sod field and doesn't know exactly
where to drop the load.
So the first step is to fence it in to make it clear to your computer and
the delivery guy where exactly the data or load of wood is supposed to go.
This is called creating the Primary partition. A Primary partition may be
sized for the entire size of your drive or just a portion of it.
When you run fdisk, the first screen will ask:
Do you wish to Enable large disk support? Choose Y if you will be installing
Windows 95B or higher.
Then select menu item 1, Create DOS partition or logical DOS drive
On the next screen select item 1 again, Create Primary DOS Partition
And just follow the prompts.
Let's say you create a Primary partition using all the space on the drive.
If you do your hard drive or Lot B will now look like this:
Exibit B. Hard drive with 1 Primary partition / aka Lot B
X X
##################################################
# #
# #
# #
# 1 Primary partition called Drive C: #
# #
# #
# #
# #
# #
# #
# #
##################################################
X X
Notice how you lost some of the capacity of the drive. The same thing
happens when you put up a fence as you have to dig the post holes and
run the fence WITHIN the boundries of your property. For example, if you
bought a 100 gig drive you now only have 95 gigs to work with.
In order to boot from this drive the Primary partition NOW has to be set
Active. During the fdisk process it "should" automatically remind you to do
this. If it doesn't one can always choose to set Active by running fdisk
again and selecting that option on the fdisk menu.
So, setting the Primary partition Active only means that you are setting it
up so it can be used to start up your computer. The only partition you need
to be set Active is the Primary partition on your first physical hard drive.
Yes there are exceptions to this for more advanced users who want to boot
from their second or third physical hard drive.
In any case your drive can now be formatted after you reboot.
Let's review:
Primary Partition - The first section on the hard drive
Set Active - Letting your computer know it can use the drive to startup
What is an Extended Partition?
As mentioned earlier, you can choose the size of your Primary partition.
Exibit B shows that the owner of the Lot or Drive only wants a single fence
or Drive letter. But what if you want to divide your hard drive or property
into 2 sections so you will have 2 drive letters for the same physical hard
drive?
Perhaps fence in a spot for your mother-in-law's trailer when she comes to
visit or create a space for your mp3 file collection. This is called
creating an Extended partition.
In order to do so you first have to create a smaller Primary partition,
perhaps using 33% of the drive. fdisk will prompt you on how large you want
to make the Primary partition. When you see the question:
"Do you wish to use the maximum available size for a Primary DOS Partition
and make the partition active?" Answer N and then put in the % you want to
use. In this example we are using 33%.
Follow the prompts then reboot. Restart and run fdisk again, choose menu
item 1 again, but this time choose menu item 2 on the next screen, Create
Extended DOS partition. You will be prompted to Enter partition size in
Mbytes or percent disk space (%). Hit Enter and it will say "Extended
DOS Partition created. Hit Escape and it will say "No logical drives defined"
Hit Enter then Escape, Escape, then reboot for it to take effect.
A hard drive with a Primary partition that only uses 1/3 of the drives
capacity and an Extended partition that uses 2/3 of the drive would look
like this:
Exibit C. Hard drive with 1 small Primary and 1 large Extended partition
X X
##################################################
# # #
# # #
# 1 Primary # #
# partition # Extended partition #
# called # No drive letter #
# Drive C: # #
# # #
# # #
# # #
# # #
# # #
##################################################
X X
OK that was a lot of information all at once as creating the Extended
partition and then creating the Logical drive within it all happens at the
same time.
To summarize graphically:
Exhibit C above shows what happened when you created the Extended partition,
or put up a fence dividing your property.
Exhibit D below shows what happened when you created the Logical drive,
which in this example puts up a SECOND fence so there is no confusion where
the boundries are.
Exibit D. Hard drive with 1 small Primary and 1 large Extended partition
with 1 Logical drive
X X
##################################################
# #LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL#
# #L L#
# 1 Primary #L L#
# partition #L Extended partition with 1 L#
# called #L Logical Drive D: L#
# Drive C: #L L#
# #L L#
# #L L#
# #L L#
# #L L#
# #LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL#
##################################################
X X
Now your hard drive has been divided into 2 usable parts, the first bootable
section is called Drive C: and the second part is called Drive D:. Drive D:
can now be formatted.
Let's review:
Extended Partition - Telling your computer you plan on using the remaining
capacity of the hard drive for data storage after you've allocated space for
the Primary partition
Logical Drive - Going through with the plan and informing your computer to
to assign a drive letter to the remaining space on your hard drive
If you want to divide your drive into MORE THAN 2 drive letters, after you
create an Extended partition and go to create the Logical Drives you will
have a choice to divide the Extended partition into 2 or more Logical
drives if you want.
This has to be done, however, when you first define the Logical partitions
or later on if you select item 3, Create Logical DOS drive(s) in the
Extended DOS partition using fdisk.
Note that if you have 2 hard drives in your computer the Primary drives
are assigned drive letters first. For example, suppose you partition your
new drive you want to boot from into 2 parts, one Primary and one Logical.
The computer will assign Drive letter C: to the first Primary partition it
sees, and then assign Drive letter D: to the second Primary partition it
sees which may be your second hard drive. The Logical drive you created
on your new hard drive would be assigned Drive E: Note that XP can bend
many of these "rules" however using Disk Management.
Why should I consider creating more than one partition?
To make your life less complicated and/or if you are only going to install
one operating system on then personally, I'd stick to one partition so you
will only have 1 hard drive letter to manage.
On the other hand here are 2 common reasons for dividing your hard drive
into 2 parts.
Reason #1. You want Windows 9X on the first partition and Windows XP on
the second partition. This will automatically give you a dual boot system
but you have to install Windows 9X first and tell XP during the install to
install to drive D:.
Reason #2. You want to save time defragging your hard drive and/or running
certain applications like anti-virus, etc. Install XP on the first partition
and use the second for your huge data files like mp3s, videos, etc. This way
you can just select the "working files" on drive C: to defrag or scan to
save lots of time.
NOTE - The biggest mistake people make when dividing their drive into 2
or more sections is that they dont make the first section, aka the
Primary partition, aka Drive C:, large enough.
Removing partitions
To remove partitions and logical DOS drives essentially you remove them
in the reverse order they were created if using fdisk. ie remove Logical
drives first, then remove Extended partition, them remove Primary partition.
##############################################
Ed Jablonowski